Acousto-Optic Modulator (AOM) has been proven to be the device of choice for many applications in laser manufacturing because it allows high performance, high laser damage threshold, low drive voltage, and low cost.
AOMs are used in lasers for Q-switching, in telecommunications for signal modulation, and in spectroscopy for frequency control. A piezoelectric transducer is attached to an acousto-optic (AO) material such as glass, quartz, or other crystals. An oscillating electric signal drives the transducer to vibrate, which creates sound waves in the AO material. By vibrating the material with a pure sinusoid so that the light is diffracted into the first diffraction order, very high diffraction efficiency can be achieved.
The rise/fall time of the AOM is an important parameter of the AOM. The rise/fall time determines how fast an AOM can be operated in high frequency demanding applications, such as Q-switch, mode locking or pulse picking in a mode lock laser. The rise/fall time of an AOM is determined by acoustic traveling time through the laser beam. The rise/fall time of the commercial state-of-the-art AOM is typically 20-100 nanoseconds (ns).
The newly emerged mode locked solid state lasers and fiber lasers generate short pulse laser with 20-80 MHz repetition frequency. For active mode-locking and pulse picking for these 20-80 MHz repetition frequency lasers, the AOM needs to have rise/fall time less than 5-6 ns. The best commercially available AOMs cannot meet the requirement for 40-80 MHz high repetition frequency laser. Even though the commercially available highest speed AOM may be used for the mode-locked lasers with repetition frequency of 20-40 MHz, the AO material cost is very high and the diffraction efficiency is low due the short optical path in the AO crystal. Accordingly, an AOM or an AO device comprising an AOM that has shorter rise/fall time than that of conventional commercially available AOM but has the same cost as conventional commercially available AOM is demanded.